Method of rolling metal sheet articles

ABSTRACT

A method of rolling metal sheet articles in which the rolls in an adjacent pair are rotated in opposite directions at different peripheral speeds under conditions of a rigid mechanical characteristic of the drive of the roll rotating at a higher peripheral speed and such a mechanical characteristic of the drive of the roll rotating at a lower peripheral speed that in the process of rolling the ratio of the peripheral speeds of the rolls is equal to the ratio of the thicknesses of the articles at input and output portions thereof before and after the rolling in the adjacent pair of rolls at a constant thickness of the output portion of the article and at a speed of movement of the output portion of the article equal to the peripheral speed of the roll rotating at a higher peripheral speed.

United States Patent [191 Vydrin et al.

[111 3,811,307 i 51 May21, 1974 METHOD OF ROLLING METAL SHEET ARTICLES Filed: June 28, 1971 Appl. N0.: 157,256

U.S. Cl. 72/205, 72/366 Int. Cl B2lb l/00, Field of Search 72/205, 232, 199, 366

[56] References Cited UNITED STATES PATENTS 5/1966 Franek 72/205 X 7/l968 Franek et al. 72/205 3/1966 Coffin, .lr 72/234 X l0/l950 Stone 72/205 OTHER PUBLICATIONS L. S. Coffin, .lr., Status of Contact-Bend-Stretch Rolling, Journal of Metals, Aug. 1967, pp. 14-22.

Primary Examiner-Milton S. Mehr Attorney, Agent, or Firm-Holman & Stern [5 7] ABSTRACT A method of rolling metal sheet articles in which the rolls in an adjacent pair are rotated in opposite directions at different peripheral speeds under conditions of a rigid mechanical characteristicof the drive of the roll rotating at a higher peripheral speed and such a mechanical characteristic of the drive of the roll rotating at a lower peripheral speed that in the process of rolling the ratio of the peripheral speeds of the rolls is equal to the ratio of the thicknesses of the articles at input and output portions thereof before and after the rolling in the adjacent pair of rolls at a constant thickness of the output portion of the article and at a speed of movement of the output portion of the article equal to the peripheral speed of the roll rotating at a higher peripheral speed. i

1 Claim, 2 Drawing Figures 1 METHOD OF ROLLING METAL SHEET ARTICLES The present invention relates to a method of rolling metal sheet members, for example, strips, bands, sheets, foil, preferably for cold rolling of these articles.

Known in the art is a method of rolling metal sheet articles (Application in Britain No. 29255, in the USA No. 836851, now Pat. No. 3,709,017) in which an adjacent pair of rolls are rotated in opposite directions at different peripheralspeeds, while tensile forces are applied to the input and output portions of the articles by means of successively enveloping the rolls by thearticles with said peripheral speeds of the rolls having a ratio equal to the ratio of the thicknesses of the article before and after the rolling in the adjacent pair of rolls and at the speed movement wherein the output portion of the article is equal to the peripheral speed of the roll rotating at the higher peripheral speed.

As the initial blank always varies in thickness in a longitudinal direction, according to this method, the drawback is eliminated or reduced by controlling the ratio of the peripheral speeds of the rolls in accordance with the change in the thickness at the input portion of the article to be rolled. This is usually effected by means of an automatic system for controlling the process of rolling, said system being very complicated and expensive.

An object of the invention is to provide a method of rolling metal sheet articles between the driving rolls which would make it possible either to eliminate or to reduce the longitudinal draw-back of the article being rolled without using an automatic system of control the rolling process. I

This and other objects are accomplished by a method which proposes to roll the metal sheet articles between the driving rolls ofa rolling mill in which the rolls in an adjacent pairare rotated in opposite directions at different peripheral speeds, tensile forces being applied to the input and output portions of the article by successively enveloping the rolls by the article with the ratios of the peripheral speeds of the rolls and being equal to ratios of the thicknesses of the article before and after rolling it in the adjacent pair of rolls with a speed of movement of the output portion of the article being equal to the peripheral speed of the roll rotating at a higher peripheral speed. According to the invention, the mechanical characteristic of the drive of the roll rotating at a higher peripheral speed is absolutely rigid, or close to it while the mechanical characteristic of the drive of the roll rotating at a lower speed is selected so that in the process of rolling the ratio of the peripheral speeds of the rolls would be equal to the ratio of thicknesses of the article at the input and output portions thereof, the output portion of the article having a constant or almost constant thickness.

The present invention provides a method of rolling metal sheet articles between the driving rolls which makes it possible either to eliminate or to reduce the draw-back ofthe article being rolled by means ofa selfcontrollable process without using any automatic system for controlling the process of rolling.

Other objects and advantages of the invention will be apparent from the following detailed description of one particular embodiment of the invention, reference being made .to the accompanying drawings, in which:

istics of the drives of the rolls during the method of rolling metal articles according to the invention.

When effecting the proposed method of rolling metal sheet articles the rolls 1 and2 (FIG. 1) are rotated by drives (not shown) in opposite directions at different peripheral speeds V, and V The roll 1 is rotated at a higher peripheral speed than the roll 2. The ratio of the peripheral speeds of the rolls 1 and 2 is equal to a ratio of the thicknesses of the article m before and after the rolling in the adjacent pair of the rolls 1 and 2, Le. V V h,,/h,. The direction of rolling the article is shown by arrows in FIG. 1. To reduce the tension P, of the output portion of the article m and the tension P of the input portion of the article the latter is bent about the rolls 1 and 2 utilizing the static friction forces F, and F against arcs AB and CD by bending the articles m over the rolls thus providing the necessary forces P,a and P a to accomplish deformation in the region of BEDG. The static friction is a force when the article is moved over the roll without sliding. Inasmuch as the static friction forces F, and F on the arcs of the bending rolls 1 and 2 by the wrapping of the article in therearound can be changed within a wide range while using the same tensions P, for the output portion of the article and P, for the input portion of the article m, the process of rolling will be stable, i.e., without sliding of the article on the arcs AB and CD of bending the rolls 1 and 2.

The diagram in FIG. 1 may be used for evaluation of the action of forces 1 within the'origin of deformation in the process of deformation: the friction forces r at the opposite contact surfaces BE and DG of the origin of deformation are equal and oppositely directed so that the pressure acting on the rolled article m side rolls the rols is considerably reduced. The drive of roll 1 rotated at a higher peripheral speed V, operates under active (driving) conditions, i.e., provides for a torque coinciding with the direction of rolling, while the drive of roll 2 rotated at a lower peripheral speed V operates under reactive (braking) conditions, i.e., creates a torque reverse to the direction of rolling.

The initial blank of the article m" always has different longitudinal draw-back i.e., the thickness h, of the article before the rolling is different in various places at input. To obtain sheet articles of a high quality it is necessary that the thickness of the article after the rolling is equal in all portions of featuring insignificant deviations from the predetermined constant thickness h,.

For this purpose, the mechanical characteristic of the drive roll 1 rotated at a higher peripheral speed is made absolutely or almost absolutely rigid, while the mechanical characteristic of the drive of roll 2 rotated at a lower peripheralspeed is selected such that in the process of rolling the ratio V,/V of the peripheral speeds of rolls 1 and 2 is equal to the ratio h /h, of the thicknesses of the article m at the input and output portions thereof at a constant or near constant thickness [1, of the output portion of the article m.

FIG. 2 shows a mechanical characteristic 3 of the drive of roll 1 rotated at a higher peripheral speed and a mechanical characteristic 4 of roll 2 rotated at a lower peripheral speed. The drive of the roll 1 has an absolutely rigid mechanical characteristic 3, Le, the rotational speed of roll 1 does not change with a change of the load (torque). The drive of the roll 2 has a soft (less rigid) characteristic 4, i.e., any increase in the load on the roll 2 is associated with a decrease in its rotational speed ensured by its drive,

.When rolling the input portion of the article m having a rated thickness h the drive of roll 1 is loaded by the torque M while drive of the roll 2 is loaded by the torque M ln this case the number of revolutions per minute of the drive of roll 1 is equal to n,, while the numb er'of revolutions per minute of roll 2 is equal to n;. If the thickness of the input portion of the article m exceeds the rated thickness h,,, the load on drives of the rolls 1 and 2 increases; the drive of the roll I develops a torque M,a, while the drive of the roll 2 develops a torque M a. In this case the number of revolutions of the drive of roll 1 is not changed (n n while the number of revolutions of the drive of roller 2 is reduced 2 "2" l- Therefore, the peripheral speed of roll 1 is unchanged (V, V,a), while the peripheral speed of roll Av /V sil /h having a constant thickness h the relative change in 2 is reduced (V, V2). Due to this fact the ratio ofthe peripheral speeds'of rolls 1 and 2 increases in accordance with the change in the thickness h of the input portion of the article m.

When the thickness 12,, of the input portion .of the article is increased for a. value 8 11,, while the peripheral speed of roll 2 is decreased for a value A V we will get the following equation (on condition that the thickness of the article after rolling is equal to the predetermined value 11,)

ing into account that lull! V V and converting the equality (2), we get the peripheral speed of the roll 2 should be equal to the relative change in the thickness h of the input portion of the article.

Thus, the proposed invention may sharply reduce the longitudinal draw-back of the ready sheet article and thus obtain a high-quality product. The absence a complex and expensive system for automatically controlling the process of rolling makes it possible to reduce the cost of the rolling mill and the expenses producing sheet metal articles.

The test rolling of metal bands having a thickness of 2 to 0.05 mm from carbon and alloyed steels according to the proposed method has confirmed the advantages and promises of this method of rolling metal sheet articles.

We claim:

1. A method of rolling metal sheet articles between the driving rolls ofa rolling mill in which the rolls in an adjacent pair are rotated in opposite directions at different peripheral speeds while providing for a rigid or close to rigid mechanical characteristic of the drive of the roll rotating at a higher speed, whereby said higher speed is maintained under conditions of varying torque. and such a mechanical characteristic of the drive of the roll rotating at a lower peripheral speed, that its peripheral speed varies inversely with variations in the load thereon due to longitudinal variations in thickness of the input portion of the article, so that, during the rolling. the ratio of the peripheral speeds of the rolls is variable so as to be maintained equal to the ratio of the thicknesses of the article at the input and output portions thereof before and after the rolling in the adjacent pair of rolls at a constant or close to constant thickness of the output portion of the article, and at a speed of movement of the output portion of the article equal to the peripheral speed of the roll rotating at a higher peripheral speed, tensile forces being applied to the input and output portions of the articles by successively enveloping the rolls by the article, first on said roll rotating at said lower peripheral speed, and then on said roll rotating at said higher peripheral speed. 

1. A method of rolling metal sheet articles between the driving rolls of a rolling mill in which the rolls in an adjacent pair are rotated in opposite directions at different peripheral speeds while providing for a rigid or close to rigid mechanical characteristic of the drive of the roll rotating at a higher speed, whereby said higher speed is maintained under conditions of varying torque, and such a mechanical characteristic of the drive of the roll rotating at a lower peripheral speed, that its peripheral speed varies inversely with variations in the load thereon due to longitudinal variations in thickness of the input portion of the article, so that, during the rolling, the ratio of the peripheral speeds of the rolls is variable so as to be maintained equal to the ratio of the thicknesses of the article at the input and output portions thereof before and after the rolling in the adjacent pair of rolls at a constant or close to constant thickness of the output portion of the article, and at a speed of movement of the output portion of the article equal to the peripheral speed of the roll rotating at a higher peripheral speed, tensile forces being applied to the input and output portions of the articles by successively enveloping the rolls by the article, first on said roll rotating at said lower peripheral speed, and then on said roll rotating at said higher peripheral speed. 